SCOTUS Blog gives us the issues that the Court will resolve in official legalese:
"1. Whether the military commission established by the President to try petitioner and others similarly situated for alleged war crimes in the 'war on terror' is duly authorized under Congress's Authorization for the Use of Military Force (AUMF), Pub. L. No. 107-40, 115 Stat. 224; the Uniform Code of Military Justice (UCMJ); or the inherent powers of the President?"
"2. Whether petitioner and others similarly situated can obtain judicial enforcement from an Article III court of rights protected under the 1949 Geneva Convention in an action for a writ of habeas corpus challenging the legality of their detention by the Executive branch?"
Though the latter (Geneva Convention) question is definitely the sexier one, Steve Vladeck hints that it may be the former that ultimately sinks the Bush administration. Vladeck interprets the two main precedents, Ex Parte Milligan and Ex Parte Quirin as permitting military tribunals if and only if there is congressional authorization. The two statutory roots cited by the Bush administration above are the Authorization for the Use of Military Force (AUMF), and Article 21 of the Uniform Code of Military Justice, 10 U.S.C. 821 (UCMJ). The former, as Vladeck points out, does not ever mention military tribunals or detainees at any point. The latter reads as follows:
The provisions of this chapter conferring jurisdiction upon courts-martial do not deprive military commissions, provost courts, or other military tribunals of concurrent jurisdiction with respect to offenders or offenses that by statute or by the law of war may be tried by military commissions, provost courts, or other military tribunals. (emphasis added)
As I read this section (and I think Vladeck agrees), it means only that this statute does not supersede any other statute which would give authorization to military commissions, tribunals et al. It does not affirmatively establish those courts' jurisdiction itself. If this is the case, then the Bush administration can only justify the tribunals on the "inherent power of the presidency," which would essentially mean overruling Milligan and drastically expanding the power of the Presidency way beyond anything even considered in the past century.
One final note: While we like to cast this issue as a terrorist asserting rights in US court, I'd remind everybody that it is that very issue which is under dispute. As I wrote when the matter was before the D.C. Circuit, Hamdam disputes that he is a member of al-Qaeda, arguing that he was but a menial laborer with no ideological or structural ties to the organization writ large. He may, of course, be lying--folks accused of illegal activity have been known to do that. But that is all the more reason why we need a fair trial to determine that very relevant fact. It is repugnant to the basic principles of justice to assume his guilt prior to adjudication.